International military cooperation constitutes a vital part of states’ security policies. However, the aspect of friction in cooperation processes tends to be overlooked. Therefore, the purpose of this study is to shed light on this matter by examining the case of the Swedish Navy’s contribution to EU NAVFOR Operation Atalanta conducted in the waters off Somalia. To identify which frictions and challenges that were prominent during the operation, a qualitative methodological approach based on a theoretical framework by Nora Bensahel were implemented where Six senior officers of the Swedish Navy were interviewed about their experiences in Operation Atalanta. Results suggest that the operation in general was seen as successful but not without challenges. Sources of friction were identified in the form of conflicting national interests among participating nations, coordination efforts of parallel ongoing missions in the area, difficulties in cooperation and exchange with local authorities, as well as in national differences regarding cultural, lingual, and traditional conditions.  Some of these results are likely to be contextually dependent on the circumstances of the specific case of Operation Atalanta. Therefore, further research is required to broaden our understanding of international military cooperation from a military, operational perspective. Nevertheless, results may still make up valuable empirical contribution to such further studies.